Enable libzfs_mnttab_cache
Enable libzfs_mnttab_cache

Not setting the libzfs_mnttab_cache variable to true causes a crash in
the destruction of a temporary libzfs instance deep inside libzfs. This
is probably a bug, but easily worked around by enabling the cache, which
is also done in the zfs command line.

cbreak-black/ZetaWatch,cbreak-black/ZetaWatch